There is compelling evidence that the structure and properties of mammalian membranes are strongly dependent on lipid composition of the component bilayer. The membrane lipid composition of transformed and neoplastic cells is significantly different from that of normal cells. It has been shown in many normal cell systems that the distributions of phospholipid species, and possibly cholesterol as well, across the surface membrane bilayer is asymmetric. However, the significance and regulation of this phenomenon is not understood at this time. We propose to study four aspects of lipid asymmetry in a tumorigenic cell line, LM cells: 1. Is lipid asymmetry an intrinsic property of the cell or is it imposed on the cell by serum lipid components? 2. Can the lipid asymmetry be altered or regulated by supplementation of different lipids in the diet? 3. Are these asymmetries related to alterations in physical properties of the surface membrane, and 4. Can altered lipid asymmetry result in altered functional properties of the cell? These investigations are of significance in understanding the altered membrane properties of the neoplastic cell. Although considerable work has been done with normal cells, very little is known about lipid asymmetry of tumorigenic cells.